The present invention generally relates to a method of combining a base component and a base metal. Specifically, the present invention relates to a method of combining a metal component and a base metal of an article to form a pattern of the article, to a method of marking a metal coating, and to a method of marking a gold-plated lid of an electronic component. The present invention also relates to an article having a mark.
Most articles include one or more symbols, such as a mark. A mark may satisfy any of a wide variety of purposes, such as displaying or highlighting aesthetic value or communicating information about an article or device. For example, a mark may accent a feature of an article or may otherwise adorn an article. Also, a mark may identify an article, such as by part number, lot number, manufacturer, or date manufactured.
The Spanjer U.S. Pat. No. 4,595,647 discloses one method of marking an article. Specifically, the Spanjer patent describes a method of laser marking an electronic device that incorporates an improved material. The improved material is a plastic resin in which a filler material and a coloring material are mixed. The method includes coating the electronic device with the improved material and laser irradiating the improved material to change the color of the improved material.
Articles that are marked are sometimes coated with metal. The metal may provide a variety of desired qualities, such as abrasion resistance, improved appearance, corrosion protection, or increased strength. For example, electronic components are frequently plated with gold to minimize corrosion of underlying components. The gold plate may also ensure the electrical quality and reliability of circuitry located within the electronic components during extended periods of storage and use.
Several methods of marking metal coated articles are known. One method includes application of an epoxy-based compound to surfaces of metal coated articles. However, metal coated articles, such as electronic components used in military environments, are sometimes exposed to wide ranging environmental conditions that may include temperatures below -55.degree. C. or above +100.degree. C. Under such conditions, it has been found that epoxy-based compounds do not adequately adhere to some metal coated articles.
Another marking method involves laser etching of metal coated articles. However, laser etching is not entirely satisfactory. For instance, a laser beam may penetrate a metal coating under some conditions, such as when the metal coating is relatively thin. Penetrations in the metal coating may expose underlying metal or alloy to oxidizing environments that may corrode the underlying metal or alloy.
Another marking method involves attachment of a metal pattern to the surface of an article such that the pattern extends away from the article surface. Such metal pattern application is not always desirable since the pattern does not substantially conform to the profile of the article surface. A metal pattern that extends away from the article surface may be more easily damaged than a pattern that conforms to the profile of the article surface. Such a metal pattern may also damage items that the metal pattern contacts during use of the article.
Several techniques are disclosed for producing an article with a metal pattern. Many of these techniques include application and development of resist. For example, the Shimizu U.S. Pat. No. 5,086,013 discloses a method of placing a fine metal pattern on a substrate, such as a glass semiconductor device. Resist is applied to the substrate and silicon ions are implanted into select regions in an upper surface of the resist. The resist is irradiated with ultraviolet radiation using the implanted silicon regions as photomasks. Then, developed portions of the resist are removed using a solvent. Layers of conducting material, such as aluminum or gold, are next deposited onto the substrate and the remaining resist. The remaining resist is then removed using a solvent or plasma atmosphere to leave a desired conductor pattern on the substrate.
The Lochon U.S. Pat. No. 5,137,845 discloses a method of forming a metal contact terminal on a semi-conductor chip. The method involves placing a first mask on the chip and sequentially depositing distinct metal layers on the first mask and exposed portions of the chip. The first mask is removed and resist is then applied to the outermost metal layer and to exposed portions of the chip. A second mask is placed over the chip in alignment with the metal layers and the resist is exposed to ultraviolet light through the second mask. The developed portions of the resist and the second mask are removed, and the remaining resist pattern is used as a third mask while portions of the metal contact pad exposed by removing the developed resist are removed by etching. All remaining resist is then removed with a solvent to expose a finished metal contact terminal formed of the sequentially deposited metal layers.
The Gulla U.S. Pat. No. 5,158,860 discloses a process for selectively applying a metal pattern to the surface of a substrate. The method includes applying resist to the substrate, imaging the resist using a mask, and removing developed resist to create a desired image pattern on the substrate. The image pattern has recesses that are defined by side walls of the resist and by portions of the substrate exposed by removing developed resist. The surface layer of the remaining resist is imaged to form a surface imaged layer in the resist. Plating catalyst is then applied to the surface imaged layer and side walls of the resist and to exposed portions of the substrate. The surface imaged layer is then developed and removed to leave catalyzed surfaces solely in the recesses. Conductive metal is then deposited, using the plating catalyst, to fill the recesses and form the metal pattern. Remaining resist is imaged, developed, and removed to leave the metal pattern on the surface of the substrate.
The Tsuk U.S. Pat. No. 5,190,486 discloses an apparatus and a method for selectively plating end portions and a center portion of a conductive pen with gold and another conductive material, respectively. According to the method, end portions of the conductive pen are plated with gold. Resist is then placed on one of the end portions to mask a gold-plated region of the selected end portion. The center portion of the pen is then coated with tin-lead alloy by dipping the masked end portion and the center portion in a plating solution. The resist masking the end portion is then removed by immersion in an alkali stripping solution.
The Blacka et al. U.S. Pat. No. 5,169,057 discloses a method of soldering elements of an electronic component to an article having a gold-plated surface. First, a stream of metal particles is projected at the article at high velocity to remove gold plating from the surface of the article. Tin-containing solder is then applied to the surface cleaned of gold plate. According to Blacka et al., joining electronic component elements to a gold plated surface with tin-based solder causes embrittlement and ultimate failure of the gold-tin solder joint due to the interaction of the gold and tin. Blacka et al. provides an apparatus and method for selectively removing the gold plate to avoid the embrittlement and failure problem.